Brain lesions in man give rise to a variety of disturbances of visual cognition, including such disorders as visual agnosia, simultanagnosia and visual neglect. Though long recognized as clinical entities, the processing impairments which underlie these disturbances are poorly understood. A major goal of this research program is to provide an explanation of these phenomena in terms of a conceptual framework which has emerged from recent work on normal visual processing. The proposed investigations will focus on attentional processes, which are accorded a central role in current models of visual processing, and which have been implicated in the clinical phenomena as well. Aspects of visual information processing will also be examined in patients with acquired reading disorders, implementing new experimental paradigms developed by cognitive psychologists. In addition to contributing to the functional understanding of disorders of visual cognition, neuroimaging data will provide evidence with respect to anatomic substrates of components of the human visual processing system. Evidence from these studies will also be used to test and refine aspects of the processing model.